Such overhead conveyor systems have been known for a long time, and in this type of system it is sometimes desirable to be able to “buffer” carriages, i.e. to let a succession of carriages be stopped at a predetermined point along the rail. This may be convenient, for instance, in front of a working station or close to an elevator.
In prior-art systems, buffering is effected by extra drive sources or by different switching systems, but such solutions are expensive as well as inflexible.
It may also be the case that, depending on the type of drive, different carriages are driven at different speeds depending on different loads and/or differences in tolerances. It is then desirable for the drive of a rapidly driven carriage to cease when it “catches up with” a slowly driven carriage.
This may cause the drive of the quick carriage to slip, with increased wear and a reduced life of components included.